The Periodic Table of the Elements
Or… We Like To Organize Things
v
Origins of the Periodic Table
Dmitrii Mendeleev (1869)
• Arranged elements by atomic mass
• Elements arranged in columns had similar properties
• Many gaps, some elements out of place (ie. Nickel and Cobalt)
• Not the first to arrange elements, but first to publish and accurately predict
elements in the gaps
Henry Moseley (1913)
• Discovered relationship between the number of protons in the nucleus and
the atomic number
• Led to the development of the current Periodic Table
The Periodic Law states:
• When elements are arranged in order of increasing atomic number, their
physical and chemical properties show a periodic pattern.
Organization of the Periodic Table
•
Group
• (AKA Family) Vertical columns, 1 through 18
• Determined by number of valence electrons
• Valence Electrons – the electrons in the outermost
energy level
• Period
• Horizontal rows, 1 through 7
• The outermost principal energy level
Which element is in group 14 and period 4? Germanium
Which element is in group 6 and period 5? Molybdenum
• Classes
•
Metals
•
Nonmetals
•
Metalloids (aka Semi-Metals)
Physical Properties
Metals
•
•
•
•
•
•
•
•
•
Left side of the table
Most abundant (2/3rds of the table)
Malleable – can be pounded into sheets
Ductile - can be drawn into wires
Luster – shiny
Good conductors of heat & electricity
high melting points
•
except mercury which is liquid at room temperature
Metals lose electrons to become positive ions called cations
more reactive going down and left
Francium
•
The most reactive metal ________________
Physical Properties
Nonmetals
•
•
•
•
•
•
Right side of the table
Soft or brittle
Dull
Low melting points
•
Many are gases, few are solid
•
Only one liquid nonmetal: bromine
Gain electrons to become negative ions called anions
more reactive going up and right (Noble gases excluded)
Fluorine
• Most reactive nonmetal _______________
Metalloids (semi-metals)
•
•
•
found in between metals and nonmetals (“along the
staircase”)
Properties can be metallic or nonmetallic depending
on conditions
Periodic Table Activity
1. Color the metalloids a light-red color (Boron, Silicon,
Germanium, Arsenic, Antimony, Tellurium, Astatine)
2. Color a dark brown outline around the two liquid
elements
3. Color the metals a light blue color
4. Color the nonmetals a yellow color